Pancreatic beta cells are the major extraneural site of glutamate decarboxylase expression (GAD). During culture of isolated beta cells, the GAD product, gamma amino butyrate (GABA), is rapidly released in the medium, independently of insulin. It is considered as a possible mediator of beta cell influences on alpha cells, acinar cells and/or infiltrating lymphocytes. In this perspective we investigated the regulation of GABA release by rat beta cells during a 24h culture period. Glucose was previously reported to inhibit GABA release by diverting cellular GABA to mitochondrial breakdown through activation of GABA transferase (GABA-T). In the present study, glucagon-like peptide 1 (GLP1) was shown to stimulate GABA formation at the level of GAD, its effect being suppressed by the GAD-inhibitor allylglycine and remaining unaltered by the GABA-T inhibitor gamma-vinyl-GABA. The stimulatory action of GLP1 is cyclic AMP dependent, being reproduced by the adenylate cyclase activator forskolin and the cAMP analog 6-Bnz-cAMP and inhibited by a protein kinase A inhibitor. It is dependent on protein synthesis and associated with an increased expression of GAD67 but not GAD65. The GLP1-induced stimulation of GAD activity in beta cells can elevate medium GABA levels in conditions of glucose-driven intracellular GABA breakdown, and thus maintain GABA-mediated beta cell influences on neighboring cells.